I. Types of Genetic Disorders

Transcription

1 I. Types of Genetic Disorders Sex-Linked Disorders Diseases caused by alleles on sex chromosomes Autosomal Dominant Diseases caused by dominant alleles Autosomal Recessive Diseases caused by recessive alleles

2 Inbreeding increases chances of offspring having an autosomal recessive disorder Inbreeding: mating of two closely related individuals

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4 Prefix-Suffix break it down! Nondisjunction

5 Nondisjunction: homologous chromosomes fail to separate during meiosis If abnormal gamete unites with normal gamete during fertilization, the resulting zygote will have an abnormal number of chromosomes

6 II. Detecting Genetic Disorders 1. Karyotyping Analyzes the size, shape, and number of chromosomes

7 2. Amniocentesis Amniotic fluid, containing fetal tissue, is sampled and the fetal DNA is examined for genetic abnormalities.

8 3. Ultrasound High-frequency sound waves are used to look at organs and structures inside of the body.

9 4. Pedigrees Pedigree: a family tree indicating the expression of a particular trait Can be used to determine how a trait is inherited Key: Males = Square Females = Circle Not shaded Person does not carry an allele for a trait Half shaded Person is a Carrier (only one allele) Fully shaded Person expresses the trait (two alleles)

10 III. Examples of Genetic Disorders 1. Sickle-Cell Anemia Autosomal recessive Result of a point mutation Characterized by abnormal hemoglobin which causes red blood cells to sickle leading to oxygen deprivation.

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12 Genotype SS Ss ss Phenotype Normal blood Normal blood; increased resistance to malaria Sickle cell disease

13 2. Phenylketonuria (PKU) fen-ul-ke-toe-nu-re-uh Autosomal recessive Characterized by the inability to break down phenylalanine (an amino acid) Build up of phenylalanine leads to nervous system/brain damage Requires a strict diet Babies in the United States and many other countries are screened for PKU soon after birth

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15 Understanding Rare Chromosome Disorders

16 3. Tay-Sachs Disease Autosomal recessive Characterized by inability to break down lipids. Build up of lipids in brain leads to mental deficiencies, blindness, seizures, etc. Common in Ashkenazi Jews

17 4. Cystic Fibrosis Autosomal recessive Result of the deletion of three bases in a gene Characterized by the buildup of thick mucus that blocks airways and provides breeding ground for bacteria

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19 5. Huntington s Disease Autosomal dominant Characterized by nervous system damage and uncontrollable movements

20 6. Down Syndrome What is abnormal about this karyotype?

21 Total # of Chromosomes: 47 Result of non-disjunction Trisomy-21 Characterized by distinct facial features, difficulty learning, and other medical problems (prone to leukemia, Alzheimer s)

22 Sex Chromosome Disorders What sex chromosomes does a typical male have? What sex chromosomes does a typical female have?

23 7. Turner s Syndrome What is abnormal about this karyotype?

24 Total # of Chromosomes: 45 Result of non-disjunction Absence of a sex chromosome Characterized by short stature and dysfunctional female reproductive systems

25 8. Klinefelter s Syndrome What is abnormal about this karyotype?

26 Total # of Chromosomes: 47 Result of non-disjunction Extra Sex Chromosome (XXY) Characterized by males with small testes, problems with fertility and low testosterone

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28 Genetic Disorder Pattern of Inheritance Description Hemophilia Sex-linked Recessive Clotting disorder (missing proteins) Colorblindness Sex-Linked Recessive Unable to distinguish color Duchenne Muscular Dystrophy Sickle Cell Anemia PKU Tay-Sachs Cystic Fibrosis (CF) Huntington s Disease Sex-Linked Recessive Autosomal Recessive Autosomal Recessive Autosomal Recessive Autosomal Recessive Autosomal Dominant Weakening/loss of muscle (missing proteins) Abnormal blood cell shape (oxygen deprivation) Cannot breakdown phenylalanine (amino acid) Lack enzyme to breakdown lipids for brain function Misfolded protein - build up of mucus in lungs and body Degenerative disease of the nervous system

29 Genetic Disorder Pattern of Inheritance Description Down Syndrome Nondisjunction Trisomy 21: 47 chromosomes Distinct facial features, Difficulty learning Turner s Syndrome Nondisjunction XO 45 chromosomes Klinefelters Syndrome Nondisjunction XXY 47 chromosomes Low testosterone levels, abnormally small testes Infertilite